The voltage regulator on an outboard motor does exactly what its name suggests. Voltage produced by the flywheel and stator is regulated to an appropriate charging level, usually around 13.6 volts at the battery.
On many newer and larger outboard motors, the voltage regulator also contains a rectifier. The rectifier converts the AC current produced by the flywheel and stator into DC current, which is what the battery needs for charging.
The rectifier section also helps convert the stator’s tach signal so the tachometer receives the proper pulse type and can display engine rpm correctly.
Because of where it lives in the system, the voltage regulator can be treated pretty hard. A large-output stator, such as a 40 amp unit, can place a serious load on the regulator and create a lot of heat. Some regulators are air cooled, while others are water cooled.
With a water-cooled regulator, a weak or faulty water pump can cause the regulator to overheat and burn out. In severe cases, water-cooled regulators have gotten hot enough to create a serious fire hazard.
A bad battery or a battery that is excessively discharged can also cause the regulator to overheat and fail. Since the regulator is directly connected to the stator, a regulator that burns up and shorts internally can also damage the stator.
If your outboard has a water-cooled regulator, make sure the water pump stays in good working order, and always make sure the battery is in good condition as well.
